Photographic light-sensitive material containing tellurium and process of making the same



Patented Oct. 12, 1926 UNITED "STATES PATENT OFFICE,

SAMUEL E. SHEPPARD, OF ROCHESTER, iii'EW YORK, ASSIGNOR NEW YORK, ACORPORATION COMPANY, OF ROCHESTER,

OF NEW YORK.

PHOTOGRAPHIC LIGHT-SENSITIVE MATERIAL CONTAINING TELLURIUM AND PROCESSOF MAKING THE, SAME.

Re Drawing. Original application filed June 6. 1824, Serial No. 718,411.filed January 21, 192a. Serial No. 82,846.

, This application is a division of iny prior application No. 718,411,filed June 6, 1924, for photographic light sensitive materials andprocesses of making the same, which has 6 matured into Patent 1,574,944,granted Mar.

This invention relates graphic materials.

One object of the invention is to rovide photographic emulsions,especially evelopmg-out ones, buying new or improved properties becauseof the use or presence therein of materials, the scnsitizin propertiesof which I have discovered; r ti 1 another object of m invention is toprovide procassess in which such materials are used to improvephotographic emulsions, especially developing-out ones, as regards liht-sensitiveness, by whichte'rm I include their ability to give theearliest visible impressions or image with the minimum exposure or theirability to ive densit after a 'ven exposure or both, t e usualpliotograpl i m'e'nts, being used in preparing such impressicns or imageor densi y. v further object of the invention is to provide colloid asgelatins, the usefulness of which for forminglight sensitiveespeciallydeveloping-out emulsions, greatlyincreased and controlled bymy said sensitizing materials incorporated therewith. Another object ofthe invention is to revide processes for preparing said colloid productsorintermedlates, herfobjects are,to increase the sensitiveness ofphotographic emulsions, especially develo ng-out emulsions, while whollyor partia 1y dispensing with expensive or ion and uncertain so-calledripening met ods; to enable the use of a type of gelatin havingdesirable physical qualities in making a photographic emulsion of eaterlight-sensitiveness than that norma y obtainable with said gelatin; toobtain more stable emulsions through the purity of the ingredients; toincrease the light-sensitive ness of photographic emulsions,particularly developing-out ones, the grain characteristics' of whichhave already been determined to increase the general li ht-sensitivenessof such photographic emu ions throughout to the art of photoa0 is Kproducts, such for instance photographic emulsions,

Divided and this application the spectral ranges to which they are nor-.mallv sensitive; to make such, photogra hic emu sions of standardlight-sensitive c ar tellurium atom which is joined by a doublemetalloid atom (not one 4 bond to a single bond to one atom, differentatom) to up of atoms i s iesirable that of atoms be such and the otherbond to a which at least another the last mentioned group that itinduces in the compound a chemical affinity for silver halids,

for instance the compound maycombine to an apreciable extent with silverhalid to form a soluble complex salt when said atomic "roup is present.oreover, the metalloi atom to which the atom of tellurium is joined by adouble bond is in many instances. but not necessarily, a carbon atom. I

For some of the preferred examples of my invention, I select from theabove seriesthe following subseries tellurocarbamids. the correspondingcarbimids are likewise usable in prefepred examples of my invenchangedinto said cartion and are readil bamids, especially or instance inemulsions itwlll be of the alkaline or ammonia v understood that thecorrespon mg carbimids are included hereinafter when said carbamids areclaimed. These subseries of carbamids and carhimids include manycompounds containin one or more substltuent radicals, such as kyl, a l,acyl, alkyl-oxyi aryl-oxy, etc., groups. xamples are allyisotellurocyanate, allyl tellurourea. Not only can each compound of my581168 of T0 nasmun xonnx is attached. Generally it I light-senstitzersbe used alone to improve an emulsion (or colloid for an emulsion) buttwo or more of such compounds may be used together to obtain theirmutual or cumulative effects.

It is a common characteristic of the com ounds which I use, that saiddouble bon ed tellurium atom is chemically held in the molecule withintermediate firmness. Such atom does not react on silver halids asreadily asthe sulfur atom in sodium su'lfide for instance, but itseparates out more readily than the sulfur atom in ethyl mercaptan forexample. Consequently said double bonded sulfur-group atoms in mycompounds correspond roughly in the firmness with which they are held tothe firmness with which the sulfur atoms are held in the so-calledpotential mercaptans, although there is, of course, some range ofdifference in the firmness with which said double-bonded atoms are heldin the different compounds of my series. The sensitiveness o' the grainsof silver halid in emulsions has been shown to correspond to thepresence in said grains of nuclei of unstated chemical composition. I,therefore, attribute the sensitizing action of my compounds to theirformin in the emulsion grains small, mostly ultramicroscopic, nucleiwhich include silver combined with tellurium. The intermediate firmnesswith which said double-bonded atoms are held in my compounds facilitatesthis scattered formation or reaction without reacting on the whole ofeach grain. Since this deduction is not indispensable to the racticalusing of my invention, I do not WlSll to be limited to it except asdefined in the claims.

I have also found that the proportions in which my compounds areincorporated in the emulsions (or in the colloids for the emulsions) areimportant. If used in too high concentrations, they cause fog, andsometimes reversal. The largest proportions which can be effectivelyused vary somewhat with the particular sensitizin compound or com oundswhich are use with the roportion of gelatin to silver hahd in theemulsion, with the type of emulsion as regards grain sizecharacteristics and alkalinity, with the amount of natural sensitizeroriginating in the gelatin when the latter is manufactured, with theparticular silver halid or halids employed, the standard as regards fogwhich it set by the emulsion maker, etc. This maximum proportion is inany specific case easily found, being about as readily determined byroutine test as, for example, the proportion of sulfur permissible insteel for a particular purpose. It is, however, always surprisinglysmall. In general with gclatino-silver-halid developingout emulsions, itshould be less than about 10 grains of active sensitizing compound, in130 pounds of emulsion (the latter being computed as the weight of itsnon-aqueous ingredients in the dry state); or less that about10dgrainsin 100 pounds of gelati (com ute as dry gelatin,)' when it is adde usedin makin the emulsion. A quantity which causes immediate foggingtendency should not be used,that is, a quantity which causes more thanthe tolerated fog allowed in the particular type of emulsion in thetrade after the customarily allowed period of storage. I have found 2 to3 rains of sensitizing compound, to 100 pounds of gelatin (computed asdry) or 130 pounds of emulsion (computed as dry) is within theusefullimits and generally excellent,-say for instance with alkalinedevelopin -out gelatino-silver-hali'd emulsions. 0 course, smalleramounts of sensitizers are employed when less sensitizing effects aredesired; but it is important not to exceed the upper limits as statedabove.

Because only very minute quantities of my sensitizing compounds areused, (often less than one three hundred thousandth of the weight of theemulsion) the addition of them does not appreciably dilute the emulsionor emulsion-forming colloid; nor does it affect their physicalproperties. Consequently, the use of my compounds provides a novel,dependable, and independent way for controlling the roperties ofphotographic emulsions in a dition to the customary expedients hithertoavailable. Gelatins, for instance, can be selected for their physicalproperties, such as setting ability, melting oint and viscosity, withoutregardvto w ether they can be made into sufiiciently li ht-sensitiveemulsions, and any deficiency 1n sensitizing power can he made up byincorporating a little quantity of one or more of my independentcompounds. Nor are the grain-size characteristics affected by suchadditions of my compounds, they being independently controlled I y theemulsion maker. In other words, I can establish a ratio of sensitizingcompounds to silver halid in the emulsions which is independent of theratio of gelatin to silver halid. Still differently stated, thesensitiz-er compounds can be added without adding any colloid, such asgelatin, and are, therefore, independent thereof.

My sensitizin compounds act as so-called chemical sensitizers instead ofas optical sensitizers. In other words, they increase the eneralsensitiveness of photographic emulsions, notably developing-out ones, inwhich the are incorporated,that is to light of su stantially the samewave lengths as those to which the emulsion would be sensitive withoutthe incorporation of my compounds; instead of merely increasing the tothe gelatin before the latter is.

sensitiveness to some narrow group of wave lengths. Unlike the effectsof dyes, the sensitiveuess is increased throughout the normal spectralrange of the emulsion instead of at only those spectral pointscorresponding to the spectral absorption of the sensitiz ing compound.My compounds are effective in increasing the general light-sensitivenessof orthochromat-ic, panchromatic, X-ray, and all special emulsions, aswell as the ordinary or non-color sensitized ones. They can be addedwithout or with sensitizing dyes or before or after them. They do notspecifically aii ect the dye action; but simply increase the generalsensitiveness and thus in crease the ordinary sensitiveness to bluelight to at least as great an extent as to light of a colorcorresponding to the dye.

My sensitizing compounds may be used in many ways. Broadly they may beincorporated in emulsions or in colloids for emulsions or both. The canalso enter the emulsion mixed with other ingredients thereof whetherorganic or inorganic. They may be added at different stages of emulsionmanufacture, even when the latter is otherwise completely ready forcoating. Since their action is rapid when incorporated, the coating insuch case need be delayed only long enough to mix in the sensitizingcompounds. With the grain characteristics, such as size distribution.etc., already determined, and the other physical and photographicproperties of the emulsion already taken care of at this stage, I canpractically independently increase its light-sensitiveness withoutimpairing said other properties by adding one or more of my compounds.The latter are especially effective in emulsions which are, at leastslightly, alkaline.

Where difi'erent batches of emulsion, especially developing-outemulsions, fall below a required manufacturing standard of lightsensitiveness, although they may be otherwise satisfactory, theirsensitiveness can readily be brought up to standard by mixing in mysensitizing compounds, the proportion varying with the increasenecessary to produce a uniform product. Emulsions having almost nopractical light-sensitiveness but having enough other desirablequalities can be made usefully light-sensitive by m compounds. Thus thelatter are useful in connection with emulsions having good initiallight-sensitiveness and those having almost no initial sensitiveness.The increase in sensitiveness can be effected in one step by thoroughlystirring all of the sensitizing compound into the emulsion at one time;or it may be incorporated part at a time in successive ste s. Whenmaking new batches of emulsion rom the same materials which have yieldeddeficient emulsions, correctional quantities of my sensitizing compoundscan be premixed with an ingredient; such as gelatin.

The following example illustrates how light-sensitwephotographuemulsions of the developing-out type may be prepared andimproved by the aid of one or more of my sensitizing compounds. Ofcourse, my inventionis not restricted to this illustration, except asindicated in the claims. The emulsion-forming operations hereinafterdescribed are along the lines of known practice, see for instance Dielhotographie mit Bromsilber Gelatin by J. M. llder. published in Halle,Germany in 1903 by Wit helm Knapp as part III of Eders AusfiihrlichesHandbuch der Photographic."

The two following solutions are made up, the parts being by weight:

A. 900 parts of silver nitrate in 9,200 parts of water.

B. 690 parts of potassium bromide and 50 parts of potassium iodide in0,100 parts of water along with 300 parts of gelatin.

In mixing B, the halid salts are first dissolved, the water and thegelatin then added to the salt solution. Solution B is then warmed, sayto 140 F. or 150 F. for example and the silver nitrate solution A isgradually added to it with constant stirring. It is preferable to warmsolution A before adding it to B, say to 150 F. or 160 F. for instance.lVhen solution A has been thoroughly incorporated in solution B, thereare then added 43 parts of strong ammonia pre viously dissolved in 900parts of water. The emulsion formed by these operations is allowed tostand for a short time, say 15 minutes to a half hour for example. Then1050 parts of gelatin are dissolved in it with thorough mixing. Theemulsion is next cooled, such as by keeping in a cool space, until itsets to a firm jelly. The latter is broken up, as by shredding forinstance, and thoroughly washed to remove soluble salts, such aspotassium nitrate and any excess potassium halids. The wash water is, ofcourse, cool enough not to melt the pieces of emulsion jelly. The washedemulsion is next remelted to 100 F. and 1050 parts of water soakedgelatin are thoroughly mixed into it, the temperature then being raised,say between 120 F. and 150 F., for instance. for a short time, say a fewminutes. It is then cooled and set. It is an example of the ammonia oralkaline type of developing-out emulsion.

lWy sensitizing compounds may be usefully incorporated at any stage ofthe above described process of preparing the emulslon, even beingpremixed with solutions A or B or with ammonia or with the gelatin. atthe initial stages. When the compounds are incorporated in either apartly or wholly prepared emulsion, they are most conveniently handledby dissolving them in a solvent which is inert with respect to theemulsion and simply acts as a vehicle to help in spreading the compoundsthroughout the emulsion. So long as an even distribution of thecompounds throughout the emulsion is effected and the correct proportionof them is added, their particular concentration in the solvent orvehicle is not important. It is ood practice to keep the volume of thesolution added to the emulsion under 2% of the volume of the emulsion;but this is not indispensable. For example, where 1 part of allyltellurourea by weight is to be incorporated into 300,000 parts by weightof the above described emulsion (computed as the weight of itsnon-aqueous ingredients) the emulsion is melted, the sensitizerdissolved in ethyl alcohol or water or a mixture of them, the volume ofsaid solvent being under approximately 1.5% of the volume of the meltedemulsion, and then the solution is thoroughly mixed into the emulsion.When necessary to minimize dilution, the volume of solution can be kepteven below a fraction of I may mention also as very useful potassiumtellurocyanide.

With its light-sensitiveness increased by my compounds, the emulsion,being melted to the desired flowability, is coated on its support suchas glass, film, paper, etc., in the well known way. It is convenient tocontrol and check the process by coating samples of the emulsion beforeand after the addition of my sensitizing compounds, the coated specimensbeing tried out photographically by any well known sensitometric test,or even by comparative camera exposure on the same subject under likeconditions. Of course, the usual precautions are observed during theemulsion making and coating processes, such as the use of non-actinic orsafe light, cleanness of vessels and air, etc.

The different gelatines sold for photographic emulsion-making may beused in the example given above, hard ones being very useful. Thetemperatures given are, of course, adjusted if the particular gelatinemployed has physical properties, such as meltmg and setting points,which deviate considerably from the usual ones, such adjustment being amatter of routine control.

Instead, however, of using gelatins which give emulsions of useful butlower sensitiveness even before the addition of m sensitizing material,an almost inert ge atin may be employed,-one which forms an emulsionwhich produces a developable image, if at all, only after impracticallylong exposures, and then does not yield an ima e of desirable density. Agelatin which orms such a practically inert emulsion may be prepared inthe way described under the heading Preparation of ash-free gelatin inpages 1856 and 1859 of the Journal of the American Chemical Society,September, 1922, vol. XLIV, No. 9, bemgpart of an article by Sheppard,Sweet, and Benedict on Elasticity of purified gelatin jellies as afunction of hydrogen-ion concentration. Emulsions of impractically lowlight-sensitiveness made by the above described process from suchprepared gelatin, are transformed by my sensitizing compounds intoemulsions which give developable ima es of excellent density afterusfully brie exposures. have, for example, been able to increase thelight-sensitiveness of some such low sensitive emulsions ten or evenover twenty times, the exposures for a given subject in the latter casebeing cut to less than one twentieth of the original one and the imagedensity being made excellent by a corresponding gain. Increases of thesame general order of magnitude are made when my sensitizing compoundsare added in similar proportions to emulsions which are made from normalphoto raphic gelatins or mixtures of such norma gelatins with saidalmost inert gelatins, and already have useful, but lower initialsensitiveness. Difierent ercenta es of sensitizer produce correspondingldifi'erent increases. The increases in deve oping-out emulsions appjearupon the usual developing operations. ustomary pyro andmetal-hydrochinon alkaline developers are suitable for example. An inertemulsion prepared as above described is a very useful medium or standardin which to test the sensitizing properties of different compounds, asample containing the compound under test being tried outphotographically along with a parallel sample of unsensitized emulsion.

Instead of the inert gelatin prepared according to the reference givenin the preceding paragraph, I can prepare inert gelatins by treatingactive photographic gelatins with oxidizing agents. The latter oxidizethe sulfur in the sensitizing substituted (allyl) thiocarbamide orcorresponding carbimide, which occurs naturally in photographic elatins,thus converting it to a non-sensitizing compound and leaving thegelatins practically inert. Dilute aqueous solutions of a peroxide, suchas sodium peroxide (say from 5 to 10% by weight) is intimately mixedinto the gelatin and then washed out when the oxidation has occurred.The inert gelatin referred to in the preceding paragraph can be thusoxidized to make its inertness doubly sure.

When preparing inert elatin on a considerable scale, it is far preambleto introduce the oxidizing step during the regular manufaeturingoperations, say the liming and /or deliming treatments. The oxidizingagents should be efi'ective as desensitizers and yet not be present inquantities capable of materially reducing the yield of gelatin orharming its quality especially its physical pro erties. Nor s ould theyleave 0 jectiona le products from the oxidation reaction. For example,the regular liming solution of the usual gelatin manufacturing processcan be saturated with as much calcium hypochlorite as will dissolvetherein; or it can obtain about 5 to 10% of sodium peroxide. Subsequentoperations then proceed as usual.

My sensitizing compounds ma be incorporated into gelatin from which piotographic emulsions are to be made. This strengthened gelatin thenconstitutes a valuable intermediate in emulsion manufacture. While anygood gelatin may be thus treated, that which has been rendered inert bythe above described oxidation treatment during liming or deliming isarticularly adapted to this strengthening. ltmulsions made from themixture have markedly increased lightsensitiveness as compared withthose made from corresponding unstrengthened gelatins. The proportion ofsensitizing material is, of course, adjusted to give the desired controlof the sensitiveness of emulsions made from the gelatin, the totalsensitizing material in the strengthened gelatin being thus brought to,or even above, normal.

When working on a considerable scale, this activating of gelatin, such,for instance, as said inert gelatin, is one of the most desirable waysof employing my sensitizing compounds. In fact, premixing of one or moreof my sensitizers with gelatin is my preferred system. Duringmanufacture of the gelatin, say for instance when the concentratedgelatin solution comes from the evaporator before setting and drying,the sensitizing compound or compounds are added and thoroughly mixed toobtain effectively uniform distribution. For example 2 or 3 grains ofany of the hereinabove listed compounds or mixtures of them is carefullymixed with each fraction of gelatin solution containing 100 pounds ofgelatin (calculated as dry). The compound is taken up, preferably in aslittle aqueous-alcohol mixture as is practicable, and. then thisconcentrated solution added to the gelatin solution. In this Wayundesirable dilution of the latter is avoided.

On a large scale, the sensitized solution may be accurately andcontinually dosed into a regulated stream of elatin solution withcontinuous mixing. Alternately dried or set gelatin may be allowed toswell in an aqueous solution of the sensitizing compound. The nearlyuniform distribution or diffusion of the compound in the gelatin thuseffected can be made even more nearly uniform by melting and agitatingthe swollen gelatin.

In the examples given above, the steps of treating with ammonia andwarming of the emulsion just before its final setting improve thephotographic properties of the emulsion, especially when the latter ismade from hard gelatins. But one or both of them may be omitted. Inother words, my sensitizing compounds act by themselves to increase thelight-sensitiveness, whether ripening steps be employed or not, and socan wholly or partially replace them. llut I prefer to use them becausethe effect of either or both of them is to help increase thelight-sensitiveness of the emulsions and thus gives a stronger initialsensitized condition which is multiplied or increased by using mysensitizing compounds. When using any of the inert gelatins mentionedabove in making very sensitive emuls ons, these steps can sometimes beshortened and made more certain in effect by reason of the use of mypowerful and dependable sensitizing compounds.

1 have described gelatin emulsions and emphasized the developing-out andalkaline types because at the present time they are the ones which havethe widest practical use. Moreover they form the best medium for testingnew sensitizing-compounds. .llut other organic colloids and mixtures ofthem with each other or with gelatin, where their nature admits suchmixtures, may be used in making light-sensitive emulsions which can beimproved by adding my sensitizing material. Albumens, agar-agar, gums,such as gum-arabic, cellulosic derivatives such as collodion areinstanced. While I have illustrated the use of my sensitizer inconnection with such sensitive substances as silver bromide and silveriodide, other lightscnsitive substances can be employed, such as silverchlorid, alone or mixed with one or more of the others.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. A photographic developing-out emulsion comprising a colloid,particles of photographic silver salt suspended therein, and an addedcompound therein upon WhlCll at least part of the light-sensitiveness ofthe emulsion depends, said compound containing a divalent tellurium atomdirectly joined by a double bond to a single metalloid atom to which atleast another group of atoms is attached, the proportion of saidcompound being substantially independent of the proportion of saidcolloid.

2. A photographic developing-out emulsion comprising gelatin, particlesof silver halid suspended therein and telluro carbamid upon which atleast part of the lightsensitiveness of the emulsion depends.

3. A photographic developing-out emu]- sion comprising gelatin,particles of silver halid suspended therein and allyl tellurourea uponwhich at least part of the lightsensitiveness of the emulsion depends.

4. A photographic developing-out gelatino-silver-halid emulsion of thealkaline type of relatively high light-sensitiveness, comprising amixture of the contituents ot a gelatino-silver-halid emulsion of lowerlight-sensitiveness and an added sensitizing compound upon which dependsthe difference between said lower and said high light sensitiveness,said compound containing a divalent tellurium atom directly joined by adouble bond to a single metalloid atom to which at least another groupof atoms is attached.

5. A photographic emulsion comprising a colloid, particles of silverhalid suspended therein and an added compound therein upon which atleast part of the light-sensitiveness of the emulsion depends, saidcompound containing a divalent tellurium atom directly joined by adouble bond to a single metalloid atom to which at least another groupof atoms is attached, the proportion of said compound beingsubstantially independent of the proportion of gelatin, and saidemulsion being substantially free from sensitizing dye.

6. A photographic developing-out emulsion comprising a colloid,particles of photographic silver salt suspended therein, and an addedcompound therein upon which at least part of the light-sensitiveness ofthe emulsion depends, said compound containing a divalent tellurium atomdi rectly joined by a double bond to a single metalloid atom to which atleast another group of atoms is attached, the amount of added compoundbeing less than the order of 10 grains per 130 pounds of emulsion andinsufiieient to cause immediate fogging tendency.

7. In a process of preparing a developing-out gelatino-silver-halidemulsion, increasing the light-sensitiveness thereof by incorporatingwith the other constituents thereof a sensitizing compound containing adivalent tellurium atom directly joined by a double bond to a singlemetalloid atom to which at least another group of atoms is attached. 48. In the process of preparing a developing-out gelatino-silver-halidemulsion, in creasing the light-sensitiveness thereof by incorporating atelluro carbamid with the other constituents thereof.

9. In the process of preparing a developing-out gelatino-silver-halidemulsion, increasing the light-sensitiveness thereof by incorporatingallyl tellurourea with the other constituents thereof.

10. In the process of preparing a developmlg-out gelatino-silver-halidemulsion of the al alme type of relatively high light-sensit veness,combining constituents of a gelatmo-silver-halid emulsion of said typebut of lower light-sensitiveness with an independent sensitizingcompound, said compound containing a divalent tellurium atom of thesulfur group directly joined by a double bond to a single metalloid atomto which at least another group of atoms is attached.

11. In the process of preparing a developing-out colloidsensitive-silver-salt emulsion, increasing the light-sensitivenessthereof by incorporating with the other constituents thereof, which aresubstantially free from sensitizing dye, a sensitizing compound, whichis also substantially free from sensitizing dye. said compoundcontaining a divalent tellurium atom directly joined by a double bond toa single metalloid atom to which at least another group of atoms isattached.

12. In the process of preparing a developing-out gelatino-silver-halidemulsion, increasing the light-sensitiveness thereof by incorporatingwith the other constituents thereof a sensitizing compound containing adivalent tellurium atom directly joined by a double bond to a singlemetalloid atom to which at least another group of atoms is attached, theamount of said added compounds being less than the order of 10 grainsper 130 pounds of emulsion and insufiicient to cause immediate foggingtendency.

13. An intermediate for use in making photographic emulsions, comprisingan en-iulsion-forming colloid having incorporated therein a sensitizingcompound containing a divalent tellurium atom directly joined by adouble bond to a single metalloid atom to which at least another groupof atoms is attached.

14. An intermediate for use in making photographic emulsions, comprisinggelatin having incorporated therein telluro carbamid. I

15. An intermediate for use in making photographic emulsions, comprisinggelatin having incorporated therein allyl tellurourea.

16. An intermediate for use in making photographic emulsions, comprisingan emulsion-forming colloid having incorporated therein a sensitizingcompound containing a divalent tellurium atom directly joined by adouble bond to a single metalloid atom to which at least another oup ofatoms is attached, the amount 0? said added compound being less than theorder of 10 grains in 100 pounds of gelatin.

17 The process of making an intermediate for use in the preparation ofphotographic emulsions, which comprises incorporating in anemulsion-forming colloid an independent sensitizing compound containinga divalent tellurium atom directly joined by a double bond to a sin lemetalloid atom to which 'at least anot or group of atoms is attached.

18. The process of making an intermediate for use in the preparation ofphotographic emulsions, which comprises incorporating in anemulsion-forming colloid telluro carbamid.

19. The process of making an intermediate for use in the pre aration ofphotographic emulsions, whic comprises incorporating in anemulsion-forming colloid allyl tellurourea. I

20. The process of making an intermediate for use in the preparation ofphotographic emulsions, Which comprises incorporating in anemulsion-forming colloid an independent sensitizing compound containinga divalent tellurium atom directly joined by a double bond to a singlemetalloid atom to which at least another group of atoms is attached, theamount of said added compound being less than the order of 10 grains per100 pounds of said colloid (calculated as dry colloid), and beinginsufficient to cause immediate fogging tendency.

21. lhe process of making an intermediate for use in the preparation ofphotographic emulsions, which comprises incorporating in anemulsion-forming colloid telluro carbamid, the amount of said addedcompound being less than the order of 10 grains per 100 pounds of saidcolloid (calculated as dry as colloid) and being insufficient to causeimmediate fogging tendency 22. The process of making an intermediate foruse in the preparation of photographic emulsions, which comprisesincorporating in an emulsion-forming colloid allyl tellurourea, theamount of said added compound being less than the order of 10 grains per100 pounds of said colloid (calculated as dry colloid) and beinginsufficient to cause immediate fogging tendency.

23. The process of making an intermediate for use in the preparation ofhotographic gelatino-silver-halid emu sions, which comprisessubstantially freeing gelatin from sensitizing compounds, andincorporating therein a sensitizing compound containing a divalenttellurium atom directly joined by a double bond to a single metalloidatom to which at least another group of atoms is attached.

24. The process of making an intermediate for use in the preparation ofphotographic gelatino-silver-halid emulsions, which comprisessubstantially freezing gelatin from sensitizin compounds, andincorportaing therein te luro carbamid.

25; The process of making an intermediate for use in the preparation ofphotographic gelatino-silver-halid emulsions, which comprisessubstantially freeing gelatin from sensitizing compounds, andincorporating therein a sensitizing compound containin a divalenttellurium atom directly joined y a double bond to a single metalloidatom to which at least another group of atoms is attached, the amount ofsaid added compound being less than the order of 10 grains for 100pounds of gelatin (calculated as dry gelatin), and being insufficient tocause immediate fogging tendency in emulsions made from saidmtermediate.

Signed at Rochester, New York, this 18th day of January, 1926.

SAMUEL E. SHEPPARD.

graphic emulsions, which comprises incorporating in an emulsion-formingcolloid telluro carbamid.

19. The process of making an intermediate for use in the preparation ofphotographic emulsions, which comprises incorporating in anemulsion-forming colloid allyl tellurourea.

20. The process of making an intermediate for use in the preparation ofphotographic emulsions, which comprises lIICOI" porating in anemulsion-forming colloid an independent sensitizing compound containinga divalent tellurium atom directly joined by a double bond to a singlemetalloid atom to which at least another grou of atoms is attached, theamount of said added compound being less than the order of 10 grains per100 pounds of said colloid (calculated as dry colloid), and beinginsufiicient to cause immediate fogging tendency.

21. The process of making an intermediate for use in the preparation ofphotographic emulsions, which comprises incorporating in anemulsion-forming colloid telluro carbamid, the amount of said addedcompound being less than the order of 10 .grains per 100 pounds of saidcolloid (calculated as dry as colloid) and being insufficient to causeimmediate fogging tendency 22. The process of making an intermediate foruse in the preparation of photographic emulsions, which comprisesincorporating in an emulsion-forming colloid allyl tellurourea, theamount of said added compound being less than the order of 10 grains per100 pounds of said colloid (calculated as dry colloid) and beinginsufficient to cause immediate fogging tendency.

23. The process of making an intermediate for use in the preparation ofhotographic gelatino-silver-halid emu sions, which comprisessubstantially freeing gelatin from sensitizing compounds, andincorporating therein a sensitizing compound containing a divalenttellurium atom directly joined by a double bond to a single metalloidatom to which at least another group of atoms is attached.

24. The process of making an intermediate for use in the preparation ofphotographic gelatino-silver-halid emulsions, which comprisessubstantially freezing gelatin from sensitizin compounds, andincorportaing therein te luro carbamid.

25. The process of making an intermediate for use in the preparation ofphotographic gelatino-silver-halid emulsions, which comprisessubstantially freeing gelatin from sensitizing compounds, andincorporating therein a sensitizing compound containin a divalenttellurium atom directly joined by a double bond to a single metalloidatom to which at least another group of atoms is attached, the amount ofsaid added compound being less than the order of 10 grains for 100pounds of gelatin (calculated as dry gelatin), and being insufficient tocause immediate fogging tendency in emulsions made from said 1ntermediate.

Signed at Rochester, New York, this 18th day of January, 1926.

SAMUEL E. SHEPPARD.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,602,591,

granted October 12,

1926, upon the application of Samuel E. Sheppard, of Rochester, NewYork,l for an improvement in Photogra hic Light-Sensitive Material(/ontammg Ie lurlum and Processes of Making t 0 Same, errors appearinthe printed spec fication requiring correction as follows: Page 1,line 43, after the word making insert the word such;

page 3, line 22, for the article The, first occurrence, read They; page5, line rd for the word sensitized read sem'ibizingf' same pa e, line53, for the W0 Alternately read Alternatively; page 6,

page 2, line 56, after the word which insert the word is,

inc 39, claim 7, for the article a,

first occurrence, read the; page 7, line 29Tclaim 21, strike out theword as; same page, line 53, claim 24, for the Word eezing read racing;and that the said Letters Patent should be read with these corrections terein that the same may conform to the record of the case in the PatentOflice.

Signed and sealed this 28th day of December, A. D. 1926.

M. J. MOORE, Acting Commissioner of Patents.

Certificate of Correction.

It is hereby certified that in Letters Patent No. 1,602,591, grantedOctober 12, 1926, upon the application of Samuel E. Sheppard, ofRochester, New York, for an improvement in Photographic Light-SensitiveMaterial Containing Tellurium and Processes of Making the Same, errorsappear in the printed specification requiring correction as follows:Page 1, line 43, after the word making insert word such,- page 2, line56, after the word which insert the word is; page 3, line 22, for thearticle The, first occurrence, read They; page 5, line 50 for the wordsensitized read semrim'zing' same page, line 53, for the W0 Alternatelyread Alternatively; page 6, inc 39, claim 7, for the article a firstoccurrence, read the; page 7, line 29 claim 21, strike out the word as;same age, line 53, claim 24, for the word freezing read freeing; andthat the said tters Patent should be read with these corrections thereinthat the same may conform to the record of the case in the PatentOfiice.

Signed and. sealed this 28th day of December, A. D. 1926.

[emu] M. J. MOORE,

Acting Uommissiomr of Patents.

